Mercury switch



March 25, 1930. v P. K. cRAMBLr-:T l 1,751,544

MERCURY SWITCH Filed Nov. 24, 1928 INDENTOR.

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Patented Mar. 25,` 1930 UNITED sTATes PATENT 4oi-'Fica PAUL KICRAMBLET, OF MILWAUKEE, WISCONSIN, ASSIGNOR T TIME-O-STAT CONTROLS COMPANY, OF ELKHART, INDIANA, Av CORPORATION OF MARYLAND MERCURY SWITCH Application led November 24, A1928. Serial No. 321,568.

This invention relates' in general to mercury switches and more particularly to the type of mercury switches having an outer.

Y outer envelope in a simple, durable and efec-' holding the protectiveelement substantially envelope and an inner protective element supported upon the outer envelope in spaced relation thereto.

The present invention aims to provide a mercury switch of this character wherein the inner protective element usually in the form of a tube of arc resistant material is supported and maintained in proper relation to-the tive manner and in such a way as to preclude the transmission of shocks and strains between the tube and the outer envelope while rigid with respect to its envelope.

Another important object of the invention is to facilitate the production of a mercury switch of this characterand inl pursuance of this object the present inventionproposes a novel method of making this type of mercuryA A further, object is to provide a mercury switch having these advantages and capacities andwhich is of vsimple construction, which will stand up under the conditions of actual practice without disintegr'ating -and v contaminating the mercury and which iseasy and comparatively inexpensive to manufac- A ture.

` Otherobje'cts and advantages reside in certain novel 'features of the construction,`ar

' rangement and combination of parts which will be hereinafter more fully described and particularly pointed out in the 'appended claims, reference being had to the accompany-I ing drawings' forming a part of this specification, and in which: f

Figure 1 is a view, partly in central longitudinal section and partly in elevation f showinga mercury switch embodyingy the present invention, andillustrating the switch in circuit breaking position; l Figure 2'is a similar view showing the switch in circuit making position; i e Figure 3 is a view in transverse sectio taken on line 3-3 of Figurev 2; Figure i is an enlarged` fragmentary sectional view, the section being taken in the -same plane as that of4 Figures 1 and 2 but thel y showing beingsomewhat enlarged to better illustrate the construction whereby the inner tube is supported on the outer envelope; and Figure 5 1s a group view partly in section and partly in elevation illustrating the steps glass, quartz, porcelain, or any other suitable arc resistant material. For the purpose -ofh supporting the protective tube 2 upon the outer .envelope and in spaced relation thereto, novel supporting means designated generally at 3 is utilized. The supporting means 3 includes an integral or one-piece rigid ring 4 which may be of glass, aluminum-oxide, or any other molded or cast material. The glass ring 4 is covered with a coating 5 of cement which, in the assembly, adheres to the outer l periphery of the tube 2 and to the inner pe' riphery oithe envelope 1.' Electrodes 6 and 7 are sealed in through the ends of the glass envelope and are constantly immersed in material.

bodies of mercury designated 'at` Sand 9, respectively. In the closed position of the switch the bodies of mercury designated at 8 and 9 unite on a surface 2" of the hard glass i tube 2. Similarly, when the switch is moved to the circuit breaking position the bodies of mercury divide on the surface 2 ofthev glass .The steps of themethod by which this switch construction is produced are illus- -trated diagrammatically in Figure 5. As 1llustrated in Figure 5, the glass ring 4 is first coated with the covering 5 of cementitious This cementitious materialis of such character-and composition that it expands slightly when heated and sets in its expanded condition. While various cementif .tious substances may be utilized preferably the cement consists of sodium silicate 'and calcium carbonate in the proportions of four of sodium silicate, the` sodium silicate havpounds of calcium carbonate'to five gallons ing a specific ravity of 42 degrees Baume, and. having a alanced composition inthat it basa sodium oxide content of eight per cent and a silicon dioxide content of thirty per cent. The viscosity of the cement thus constituted is determined and either by drying or the addition of Water this viscosity is varied until it is appropriate for the switches to be manufactured. The glass rings 4 are coated with this cement by a series of dipping operations with alternate drying. Usually three dipping operations are required to build up the requisite coating 911 the glass ring. Where air drying is employed between the p dipping operations, the time of drying varies from 15 to 20 minutes, depending upon the prevailing humidity as determined by a hygrometer. V After the glass ring has been properly coated and dried it is assembled with one end of the protective tube 2 and the protective tube and glass ring are then inserted in the outer envelope 1 which, in its original condition, is open at both ends, as illustrated in Figure 5. The assembly is then placed in an oven and is heated to a rather high temperature, usually from 320 .to 400 degrees centigrade. The temperature of the oven is raised slowly and preferably overa period of 5 to 10 'minutes and the'temperature is held at 1 the highest `point .for approximately thirty minutes. This causes the calcium carbonate and the sodium silicate to react and set, thus forming the constituent parts of soda lime glass and evaporating the free or occluded moisture. During this heating the cement expands slightly and while the expansion is sufficient to cause the covering of cement to tightly engage and adhere," not only to its ring 4 but also to its envelope l and tube 2 the expansion is notof such amount as to crack any of the parts. lThe switch is then removed from the oven after cooling and fol lowing inspection is subjected to .an annealing operation: which consists in raising the temperature of the switch as thus far made tota point just under fusing temperature, which is usually somewhere from 500 to degrees centigrade. The temperatureis held at this point for a period ranging from 10 to 15 minutes and the switch is then slowly cooled. This relieves any strains that may .therethrough in accordance with conventional practice, the mercury placed within the 'switch through the usual tubulation or sealing tip 10 and the air exhausted and an atmosphere of'inert -gas supplied through this sealing tip after which the tip is fused and sealed. Q

A mercury switch constructed in this manner rigidly maintains the inner protective tube in proper position within the outer envelope and out of contact therewith. While the composite supporting structure is -suiiiciently rigid to maintain this relation between the parts and issuiiciently durable to sta-nd up under the conditions that result from the operation of the switch, nevertheless, the covering of the cement on the ring 4 has a yyieldable or resilient property which enables it to take up the shocks or strains resulting from arcing and precludes the transmission of these shocks and strains between the inner protectivetube and the outer envelope. And the cement thus constituted and applied will not disintegrate or contaminate the mercury and impair the support of the protective tube. The rigid ring embedded in the cement gives the composite supporting structure qualities of strength and rigidity and aids in maintainamount of yieldabilityis supplied by the cement. Further, as the adhesion of the cement to the envelope and4 protective tube results from the expansion of the cement following its heating, this adhesion is uniform over a large area to distribute the loadof support over a 'large area. of the outer envelope. While these advantages are realized, the manufacture of the switch is simpliedand may be carried out with economy. Obviously,

quitera large number of rings may be simultaneously coated .with cement by utilizing a f tray on which the rings are supported for dipping. The assembly operation consists merely of the fitting of a preparedring on the inner tube andthe intertitting of the assembled tube and ring with the glass envelope. The fixing of these parts in this position follows from the subsequent heating operation. Another` advantage of this type of suA port 1s that it prevents the mercury from lo ging therein and finding its way therethrough and producing a short-circuit, although it has sufiicient porosity to prevent entrapment of gas many zone or compartment of the switch. The ring itself, of course, has no porosity but the cement has such a limited amount of porosity to permit of the seepage of gas therethrough. However',A the cement is of such a dense and compact Vconstruction as to preclude the vmercury from nding its way therethrough or infiltratingtherein even .when the mercury is thrown against the partition under heavy pressures.

The invention claimed is 1. A-mercury switch comprising an outer envelope, an inner protective tube of arc resistant material, and means for supporting the tube on the envelope, and including a supportlng ring of glass interposed between the tube and the envelope and a body of cement covering the ring and adhering thereto and to th tube and envelope.

2. A mercuryl switch comprising an outer envelope, a protective element of a'rc resistant material in said envelope, and means for supporting the protective element on the envelope and comprising anbody Voit cement. in-

terposed between the protective element and the envelope andhaving a rigid supporting element embedded therein.

3. `A mercury switch comprising an envelope,- a protective element of arc resistant material therein, and means for supporting thef protective element on theenvelope and comprising a ri 'd -supporting element inter;

f posed between t e protective element and the envelope, and yieldable means between the rigid supporting element and the envelope and the supporting element and the protective element. t

4. A mercury switch comprising an outer envelope, a protective element of arc resistant material therein, and means for supporting the protective element on the envelope and comprising a rigidsupporting element interposed between the protective element andthe envelope, a protective element of arc resistant envelope, and a yieldable covering on. the rigid supporting element engaging the envelope and the protective element. 5. ,A mercury switch comprising an outer material therein, and means for supporting 'the protective element on the envelope and lcomprising .a supporting element yinterposed between the protective element and the envelope,l and yieldable la'yers interposedbetween and having holding engagement with the protective element and the supporting element and the envelope and the Isupporting element.

. 6. A.mercury switchcomprising an outer envelope, a protective element of arc resistant material thereinkand means for supporting the protective element on the envelope,and

5 comprising a rigid supporting element interposed between the protective-element and the envelope, and -layers of material having cementitiousJ .properties interposed between and adhering to said supporting element and said protective element. 7. A mercury switchcgmprislng an outer said envelope and said supporting element and envelope, a protective element of arc resists teo ant material therein, and means for supporting the protective 'element on the envelope and comprising a rigid supporting element interposed p between the protective element and the envelope, and/cement associated with the supporting element and actingv to main-,

,tain the protective element in position while `minimizing the transmission of shocks and f strains between the proteztive element and the envelope.

8.-In a device 'of the character described having tubular structures located one within outer the other, means for supporting one tubular structure on the other including a body of cement interposed between said structures and having a rigid supporting element em,-

bedded therein.

' 9. In a device of the character described having tubular structures located one within the other, means 'forsupporting one tubular str ucture on the. other including a lrigid supporting element interposed between said structures and vcement associated' with the supporting element and completing the supporting action thereof while minimizing the transmission of shocks and strains.

10. In a device of the character described having tubular structures located one within the other, means for supporting one tubularl soi' structure on the other including a body of yieldable adhesive material and a glass .ring embedded therein.

1l. Means for supporting an element of a mercury switch in position therein including a hard and rigid supporting member interposed between the element and the-part of the switch on which it is supported and 1ay-" coating a supporting member with a sub-v stance which expands and sets under the action'of heat, assembling the supporting'member with the-parts lof the switch structure which itis designed to maintain in proper position and relation, and subjecting the assembly to the action of heat.

f '14. The hereindescribed method of making a mercury switch structure which consists in coating a supporting member with a substance which expands and sets under the action of heat, assembling the supporting member with the parts of the switch structure which it is designedto maintain in proper pos1tion and' `relation,baking the assembly to cause. sald substance to expand and set,

-and subsequently annealing the assembly.

15. The hereindescribed method of'makinga mercury switch structure which consists in coating a supporting member with a cementitious 'substance whlch expands 'and s'ets under 'the action of heat and which when sethas suiclent yleld'ability to prevent transmissionof shocks and strains therethrou h,

assembling the coated supporting mem r with the parts .of the* switch structure it is designed to malntain 1n properposition an subjecting the assembly to heat to expand and set the covering of cement. v

16. The hereindescribed method of mak'- ing a mercury switch structure which con- .'sists 4in coating a supporting member with a cementitious substance having the property of expanding and setting under the action of heat by successively dipping the supporting member in such substance, permitting it to dry in between dipping operations, assembling the supporting'member so coated with parts f the switch structure which it is deand calcium carbonate adhering to the-ring and to the tube and to the envelope for rig- -idly holding the parts in proper position and relation while precluding the transmission of shocks and strains.

ln witness whereof, I hereto ailix my signa 70 ture.

PAUL K. CRAMBLET.

signed to maintain in proper position and relation and subjecting the assembly to heat to expand and set the cementitious coating.

17. The hereindescribed method' of making a mercury switch which consists in coating an integral supporting memberwithfa\ cementitious substance consisting of an aque-` ous solution of sodium silicate and calciumcarbonate, allowing the coating totdry, then v assembling the coated supporting member with the parts of the switch structure which it is designed to maintain in proper position and relation and subjecting the assembly to heat to cause the calcium carbonate and sodi um`silicate to react and to form the constituent partsl of soda lime glass and evaporate to free or occluded moisture whereby the coating expands and sets to rigidly maintain the parts ,of the switch in position while precluding the transmission ofshocks and strains. i

18. The hereindescribed method of making a mercury switch structure of the type having an inner protective tube" ofl arc re- -cement to expand and set to maintain the parts in proper position and relation.

19. A mercury switch of the character described including an outer envelope, an inner protective tube of arc resistant material, and a composite supporting member between the tube and, the. envelope and comprising a rigid integral ring and a coatingof cementitious material expanded inthe assembly to adhere to the ringand to the tube and to the envelope for rigidly holding the parts in f proper position and relation whileprecluding the transmission of shocks and strains.

20. A mercury switch, of the character described including an outer envelope, an inner protective tube of are resistant material, and a composite supporting member between the tube and the envelope and comprising a.

rigid integral ring and a. coating of cementitipous material consisting 'of sodium silicate' 

